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72 lines
2.3 KiB
Plaintext
72 lines
2.3 KiB
Plaintext
=pod
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=head1 NAME
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EVP_PKEY_verifyrecover_init, EVP_PKEY_verifyrecover - recover signature using a public key algorithm
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=head1 SYNOPSIS
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#include <openssl/evp.h>
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int EVP_PKEY_verifyrecover_init(EVP_PKEY_CTX *ctx);
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int EVP_PKEY_verifyrecover(EVP_PKEY_CTX *ctx,
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unsigned char *rout, size_t *routlen,
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const unsigned char *sig, size_t siglen);
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=head1 DESCRIPTION
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The EVP_PKEY_verifyrecover_init() function initializes a public key algorithm
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context using key B<pkey> for a verify recover operation.
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The EVP_PKEY_verifyrecover() function recovers signed data
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using B<ctx>. The signature is specified using the B<sig> and
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B<siglen> parameters. If B<rout> is B<NULL> then the maximum size of the output
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buffer is written to the B<routlen> parameter. If B<rout> is not B<NULL> then
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before the call the B<routlen> parameter should contain the length of the
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B<rout> buffer, if the call is successful recovered data is written to
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B<rout> and the amount of data written to B<routlen>.
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=head1 NOTES
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Normally an application is only interested in whether a signature verification
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operation is successful in those cases the EVP_verify() function should be
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used.
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Sometimes however it is useful to obtain the data originally signed using a
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signing operation. Only certain public key algorithms can recover a signature
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in this way (for example RSA in PKCS padding mode).
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After the call to EVP_PKEY_verifyrecover_init() algorithm specific control
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operations can be performed to set any appropriate parameters for the
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operation.
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The function EVP_PKEY_verifyrecover() can be called more than once on the same
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context if several operations are performed using the same parameters.
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=head1 RETURN VALUES
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EVP_PKEY_verifyrecover_init() and EVP_PKEY_verifyrecover() return 1 for success
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and 0 or a negative value for failure. In particular a return value of -2
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indicates the operation is not supported by the public key algorithm.
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=head1 EXAMPLE
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Recover digest originally signed using PKCS#1 and SHA256 digest:
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[to be added]
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=head1 SEE ALSO
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L<EVP_PKEY_CTX_new(3)|EVP_PKEY_CTX_new(3)>,
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L<EVP_PKEY_encrypt(3)|EVP_PKEY_encrypt(3)>,
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L<EVP_PKEY_decrypt(3)|EVP_PKEY_decrypt(3)>,
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L<EVP_PKEY_sign(3)|EVP_PKEY_sign(3)>,
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L<EVP_PKEY_verify(3)|EVP_PKEY_verify(3)>,
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L<EVP_PKEY_derive(3)|EVP_PKEY_derive(3)>
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=head1 HISTORY
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These functions were first added to OpenSSL 0.9.9.
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=cut
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